Research On The Power Interface Algorithm Of Power Hardware-in-the-loop Simulation For MMC-HVDC

In recent years,modular multilevel converter-based high voltage direct current transmission(MMC-HVDC)has developed rapidly,and is suitable for new energy access,urban power grid interconnection and other fields.In order to deeply study the interaction between flexible high voltage direct current transmission system and AC system,traditional digital simulation methods can not meet the requirements of higher calculation accuracy and simulation efficiency;the scale of dynamic physical simulation is limited,and it is difficult to achieve full-scale dynamic simulation of complex AC/DC hybrid system.Thus,the digital physical hybrid simulation technology,also known as power hardware-in-the-loop(PHIL)simulation,was born.It is the key means to model and simulate AC/DC hybrid system with modular multilevel converter-based high voltage direct current transmission.The key of PHIL simulation lies in the power interface algorithm.The stability and accuracy of the interface algorithm are the core issues of PHIL simulation.In this paper,an improved voltage source ideal transformer method and a simplified damping impedance method for modular multilevel converter-based high voltage direct current are proposed.Firstly,the overall structure and equivalent modeling method of PHIL simulation of modular multilevel converter-based high voltage direct current transmission are studied and analyzed,and the influence of power interface on stability and accuracy of hybrid simulation system is pointed out.The operation principles of ideal transformer method and damping impedance method are analyzed,and the simplified damping impedance method is obtained.Through simulation and comparison in simple system,two algorithms are obtained in physical side and in damping impedance method respectively.Secondly,combining the advantages of the two algorithms,the interface algorithm of voltage source ideal transformer method and simplified damping impedance method is obtained,and the operation principle of the algorithm is analyzed.By establishing the Thevenin equivalent model of MMC in unlocking mode and blocking mode,the expression of equivalent impedance of physical side is obtained,impedance matching is realized and improved.Interface algorithm;Aiming at the problem of accuracy caused by interface delay,two methods of interface delay compensation are proposed,which increase phase advance correction unit and delay link respectively to improve the accuracy of PHIL simulation.Finally,a PHIL simulation system of double-end back-to-back modular multilevel converter-based high voltage direct current transmission using improved voltage source ideal transformer method and simplified damping impedance method is built in PSCAD/EMTDC.The stability of the interface algorithm is validatedunder different transient operation conditions,and the effectiveness of the proposed interface delay compensation method is verified by comparing the simulation errors before and after compensation.